OCT (Optical Coherence Tomography) devices are interferometers utilizing low-coherence light. OCT devices can detect the intensity distribution of reflected or scattered light at a position specified by a position resolution of about a coherence length in the propagation direction of the light, so as to produce a tomographic image. For example, OCT devices may be used for a diagnosis of eye, tooth, or the like. Patent Literature 1 discloses technology for using an OCT device for ophthalmic diagnosis. In the OCT device disclosed in Patent Literature 1, a light source for emitting light having a wavelength within the near-infrared region is used, and a CCD (Charge Coupled Device) imaging device is used as a photodetector for detecting light having a wavelength within the near-infrared region.